At a time when the reputation of News of the World journalists is at rock bottom, it needs to be said that the paper's former showbusiness correspondent Sean Hoare, who died on Monday, was a lovely man.

In the saga of the phone-hacking scandal, he distinguished himself by being the first former NoW journalist to come out on the record, telling the New York Times last year that his former friend and editor, Andy Coulson, had actively encouraged him to hack into voicemail.

That took courage. But he had a particularly powerful motive for speaking. He knew how destructive the News of the World could be, not just for the targets of its exposés, but also for the ordinary journalists who worked there, who got caught up in its remorseless drive for headlines.

Explaining why he had spoken out, he told me: "I want to right a wrong, lift the lid on it, the whole culture. I know, we all know, that the hacking and other stuff is endemic. Because there is so much intimidation. In the newsroom, you have people being fired, breaking down in tears, hitting the bottle."

He knew this very well, because he was himself a victim of the News of the World. As a showbusiness reporter, he had lived what he was happy to call a privileged life. But the reality had ruined his physical health: "I was paid to go out and take drugs with rock stars – get drunk with them, take pills with them, take cocaine with them. It was so competitive. You are going to go beyond the call of duty. You are going to do things that no sane man would do. You're in a machine."

While it was happening, he loved it. He came from a working-class background of solid Arsenal supporters, always voted Labour, defined himself specifically as a "clause IV" socialist who still believed in public ownership of the means of production. But, working as a reporter, he suddenly found himself up to his elbows in drugs and delirium.

He rapidly arrived at the Sun's Bizarre column, then run by Coulson. He recalled: "There was a system on the Sun. We broke good stories. I had a good relationship with Andy. He would let me do what I wanted as long as I brought in a story. The brief was, 'I don't give a fuck'."

He was a born reporter. He could always find stories. And, unlike some of his nastier tabloid colleagues, he did not play the bully with his sources. He was naturally a warm, kind man, who could light up a lamp-post with his talk. From Bizarre, he moved to the Sunday People, under Neil Wallis, and then to the News of the World, where Andy Coulson had become deputy editor. And, persistently, he did as he was told and went out on the road with rock stars, befriending them, bingeing with them, pausing only to file his copy.

He made no secret of his massive ingestion of drugs. He told me how he used to start the day with "a rock star's breakfast" – a line of cocaine and a Jack Daniels – usually in the company of a journalist who now occupies a senior position at the Sun. He reckoned he was using three grammes of cocaine a day, spending about £1,000 a week. Plus endless alcohol. Looking back, he could see it had done him enormous damage. But at the time, as he recalled, most of his colleagues were doing it, too.

"Everyone got overconfident. We thought we could do coke, go to Brown's, sit in the Red Room with Paula Yates and Michael Hutchence. Everyone got a bit carried away."

It must have scared the rest of Fleet Street when he started talking – he had bought, sold and snorted cocaine with some of the most powerful names in tabloid journalism. One retains a senior position on the Daily Mirror. "I last saw him in Little Havana," he recalled, "at three in the morning, on his hands and knees. He had lost his cocaine wrap. I said to him, 'This is not really the behaviour we expect of a senior journalist from a great Labour paper.' He said, 'Have you got any fucking drugs?'"

And the voicemail hacking was all part of the great game. The idea that it was a secret, or the work of some "rogue reporter", had him rocking in his chair: "Everyone was doing it. Everybody got a bit carried away with this power that they had. No one came close to catching us." He would hack messages and delete them so the competition could not hear them, or hack messages and swap them with mates on other papers.

In the end, his body would not take it any more. He said he started to have fits, that his liver was in such a terrible state that a doctor told him he must be dead. And, as his health collapsed, he was sacked by the News of the World – by his old friend Coulson.

When he spoke out about the voicemail hacking, some Conservative MPs were quick to smear him, spreading tales of his drug use as though that meant he was dishonest. He was genuinely offended by the lies being told by News International and always willing to help me and other reporters who were trying to expose the truth. He was equally offended when Scotland Yard's former assistant commissioner, John Yates, assigned officers to interview him, not as a witness but as a suspect. They told him anything he said could be used against him, and, to his credit, he refused to have anything to do with them.

His health never recovered. He liked to say that he had stopped drinking, but he would treat himself to some red wine. He liked to say he didn't smoke any more, but he would stop for a cigarette on his way home. For better and worse, he was a Fleet Street man.